In internal combustion engines such as diesels utilizing turbochargers, variations in engine speeds and torque demands are oftentimes important factors bearing on the efficient and safe operation of an engine when operating within its normal operating range. When operating at or above the high end of such operating range, internal pressures within the engine become very high whereby special high pressure seals and the like are required in order to prevent frequent and serious breakdowns of the engine. Furthermore, the initial and maintenance costs of such engines are inordinately high.
In an attempt to overcome these problems, various apparatus have heretofore been provided which cause a portion of the exhaust gas to bypass the turbine particularly during certain operating speeds. Such apparatus, however, because of various inherent design characteristics have been beset with one or more of the following shortcomings: (a) they are initially expensive and require substantial maintenance and service costs; (b) they are bulky and awkward to install; (c) they are incapable of effecting exhaust braking of the engine when required; and (d) they are incapable of effectively operating under engine operating conditions which vary over a wide range.